The presence of uranium (U) in wet-process phosphoric acid has been well established and various attempts to recover this valuable material have been made over the years. In the mid-1950's various precipitation and solvent extraction methods were attempted with varying degrees of success. The discovery of lower cost deposits of uranium in the western U.S. resulted in loss of interest in phos-acid (P2O5) as a uranium source at that time.
With the subsequent growth in the nuclear power industry and concerns of potential uranium supply shortfalls, interest rekindled in the early 1970's and as a result several uranium recovery facilities were constructed and utilized better solvent extraction methods, primarily based on the so-called DEPA-TOPO process that was developed at the Oak Ridge National Laboratory (ORNL). At that time, there was interest in having a non-solvent extraction system that would eliminate some of the operational issues associated with the solvent extraction systems. Unfortunately, there were no continuous contacting systems deemed applicable to this task, thus solid/liquid contacting techniques were not investigated to any great extent.
With the subsequent decline in the U3O8 from the phos-acid (P2O5) industry in the 1990's, there was little commercial-oriented interest in alternate recovery techniques, although some work continued at an academic and research level. With the resurgence of the uranium industry in the early to mid-2000 decade, opportunities now exist for advanced and/or simplified techniques to recover uranium from this important source.
Ion exchange was and continues to be a popular method for uranium recovery from more conventional aqueous uranium-containing sources, i.e. copper tailings, leached sandstone ores, etc. The use of fixed bed ion exchange contacting systems has been established in some of the conventional hydrometallurgical industries, such as uranium, and indeed has proven effective for the recovery of uranium from various sulfate and carbonate solutions.
In the early 1980's a continuous ion exchange system was developed that was originally applied to the treatment of solutions containing higher concentrations of salts or processing requiring the regeneration of relatively large quantities of ion exchange resin per unit of process fluid treated. Conventional fixed bed systems have historically had limitations when it comes to some of these unique applications. The development of the continuous ion exchange system came after the decline in the uranium from phosphoric acid industry. Thus there was little interest in the application of this advanced contacting technology to phosphoric acid as a uranium source.
As a result of the resurgence in the demand for uranium from any source, phosphoric acid sources are again being evaluated, especially in light of growth forecasts of uranium demand outstripping supply over the next several decades. Thus, there is a renewed interest in recovering uranium and the possibility of applying advance continuous ion exchange techniques is now an opportunity. A method for uranium recovery from wet-process phosphoric acid would be beneficial to the industry as a result of the inherent safety, capital and operating cost advantages that would be useful to the phosphoric acid and uranium industries.